now reads first arg as markdown

app/Main.hs

@@ -1,8 +1,14 @@
 module Main where
 
 import Lib
+import System.Environment
 
 main :: IO ()
 main = do
-        md <- readFile "test.md"
+        args <- getArgs
+        case args of
+          [fn] -> do
+                  md <- readFile fn
                   sequence_ $ sequence . fmap print <$> getMails md
+          _ -> do
+                print "please call with markdown-file"